Well, since you asked...
Had a play in both ships (FDS and Crusader), with a mixture of unengineered parts and stuff I had lying around.
Fortunately, the results didn't really highlight anything that might be improved by engineering.
First, there's the Crusader.
If you want to mine 64t of ore slowly, and shoot at anything that comes to bother you, it's the ship for you.
As a mining ship, it's a bit of a "dead end", though.
What I mean is, cos it's only got those 2 C6 slots, you're going to put a cargo rack in one and
something else in the other one.
If the "something else" is a shield, 64t of ore is your maximum and you can only run 4x Collectors... which is slow.
If the "something else"
isn't a shield, you can either fit another cargo rack and collect up to 128t slowly or you can fit a C5 limpet Controller and collect 64t at a half-decent rate.
Only trouble, there, is without the shield your canopy is a serious weak point which isn't helpful in combat and means you don't actually
need those defensive hardpoints any more cos you'll be running away instead.
Also, you can really only squeeze a C1 Prospector into it, which some might be okay with but most miners like to be able to tag at least two roids at a time.
Then there's the FDS.
This is a bit more interesting (to use, if not to look at).
You
can configure it in a similar way to the Crusader, with 64t of cargo, 2x C5 Collectors (C3s on the Crusader) and a C3 Prospector (C1 on the Crusader) - which is all good.
On the down side, it only has one "spare" hardpoint for a defensive weapon - which is not so good.
However...
Since it's not especially fighty with a single weapon, you
can get rid of that weapon completely and replace it with another mining laser.
Once you've done that, you
can get rid of the shield too, which frees up a C6 slot.
Bung another cargo rack in there and you can collect 128t of ore, or you can bung a C5 Collector in there to collect 64t of ore very speedily.
In my test-drive, the Crusader did okay but my main issue was that I can see no way to really improve it further.
The FDS hoovered up 64t of ore in about 15 minutes, went back to my FC, fitted another mining laser and another cargo rack and (unsurprisingly) it can collect 128t of Ore in about half an hour.
It
does irk me that I can't explode pirates but, meh.
Ultimately, the FDS doesn't have the same potential, as a mining ship, as the Python or Krait but, in it's own right, it
does make a half-decent little mining ship.
The problem I now have, though, is that my original intention was to build a
fighty mining ship.
If I'm going to abandon that requirement, I might as well just use a Python, throw mining tools in all 5 hardpoints and end up with a more capable medium-pad laser-mining ship.